Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description contributes by disclosing what the response contains (mailboxes, renewal date, price, IMAP/SMTP config), which is genuine added value. It does not disclose pagination, ordering, or whether all purchased domains are returned at once.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single front-loaded sentence with no filler; every clause names content that is actually returned. It is a noun fragment rather than a verb-led statement, which slightly weakens the framing but wastes nothing.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no parameters and no output schema, the description carries the burden of describing return values, and it does enumerate the main fields. Only minor gaps remain — ordering, volume, and whether mailboxes are nested per domain — which matter little for a no-arg listing tool whose annotations already cover safety.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so the baseline is 4 and there is nothing for the description to disambiguate. The schema is trivially complete with no additionalProperties.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific resource — domains bought in the domain shop — and enumerates the payload (hosted mailboxes, renewal date, price, IMAP/SMTP settings). The 'bought' qualifier implicitly separates it from search_domains and buy_domains, though no sibling is named explicitly. An agent can tell what this returns without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no statement of when to use this tool versus list_mailboxes, list_dns_records, list_workspaces, or domain_health. Usage can only be inferred from the noun phrase. No prerequisites, exclusions, or alternative routing are provided.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.